Hinged crane boom stops having controlled braking means

ABSTRACT

Disclosed is a boom stop arrangement for a crane having a superstructure and a boom pivotally connected thereto for movement in a vertical plane. The boom stop consists of a first strut pivotally connected to the crane superstructure, a second strut pivotally connected to the boom, with the ends of the first and second struts pivotally interconnected, and braking means to control the rotation of one of the struts about its pivotal point. The second strut may include a spring section to provide resiliency and to absorb shock forces. Preferably, the control of the braking means is automatic and operates simultaneously with the boom elevating controls so that the brakes are applied at all times except when the boom is being raised or lowered under operator control.

[ Mar. 7, 1972 [54] HINGED CRANE BOOM STOPS HAVING CONTROLLED BRAKING MEANS [72] inventor: Ralph Mooney, Mooney Bros. Supply Co.,

133 Mahoning Avenue, New Castle, Pa. 16103 [22] Filed: Sept. 14, 1970 [21] Appl.No.: 71,874

3,092,261 6/1963 Nesbit ..212/3l9 3,123,223 3/1964 Markwardt ..2l2/59.1

Primary Examiner-Harvey C. Hornsby Attorney-Peter L. Klempay [57] ABSTRACT Disclosed is a boom stop arrangement for a crane having a superstructure and a boom pivotally connected thereto for movement in a vertical plane. The boom stop consists of a first strut pivotally connected to the crane superstructure, a second strut pivotally connected to the boom, with the ends of the first and second struts pivotally interconnected, and braking means to control the rotation of one of the struts about its pivotal point. The second strut may include a spring section to provide resiliency and to absorb shock forces. Preferably, the control of the braking means is automatic and operates simultaneously with the boom elevating controls so that the brakes are applied at all times except when the boom is being raised or lowered under operator control.

8 Claims, 8 Drawing Figures PATENTEDHAR 7 I972 3.647, 087

sum 1 0F 2 INVENTOR. RALPH MOON E Y l6 AGENT PATENTEDMAR 1 I972 3,647, 087

SHEET 2 [1F 2 FIG. 5

BOOM BOOM DOWN BOOM ELEVATION CONTROLS 64 IN VEN TOR.

RALPH MOONEY AGENT HINGED CRANE BOOM STOPS HAVING CONTROLLED BRAKING MEANS The present invention relates to boom cranes and, more particularly, to boom stop arrangements for such cranes which prevent upward movement of the crane boom except when the boom is being controllably raised or lowered.

The problem of overbooming has long been recognized in the art. Overbooming" is the condition which occurs when the crane boom swings upwardly to an instable position. This sudden upward movement of the crane boom may be caused by the snapping of a lifting cable, other sudden loss of the load being lifted, or other factors. When the boom swings into an unstable position, it unbalances the crane and may cause the crane to tip backwards. Obviously, this is an extremely dangerous condition which may result in severe injury to the crane operator and other personnel as well as in severe damage to the crane or to other structures.

In attempts to lessen this potentially dangerous overbooming, various arrangements for limiting the maximum upward movement of the crane boom have been proposed. One such arrangement is shown in U.S. Pat. No. 2,999,601. This arrangement consists of a compression strut which is pivotally mounted at one end to the crane superstructure and at its opposite end to a link strut which is also pivotally connected to the crane boom. The compression and link struts are of such lengths and so mounted that the outer end of the compression strut meets a receiving socket on the crane boom when the boom is raised to its maximum elevation. While such an arrangement provides a maximum upward position of the crane boom, it is not totally satisfactory since it provides no control of the boom movement below this maximum position. The lack of control over the boom in its intermediate positions is, however, undesirable since it permits the boom to move upward rapidly in the event of a breaking lifting cable, for example, so that the boom acquires substantial momentum and strikes the compression strut with substantial force. The force of impact may be sufficient to do severe damage to the crane structure. Also, since the major portion of the boom structure is above the point of contact between the boom and the compression strut, the momentum of the upper end of the boom may be sufficient to bend or buckle the crane boom.

It is the primary object of the present invention to provide a crane boom stop arrangement which is capable of both providing an upper limit of boom movement and of controlling and restraining the movement of the boom in any intermediate position.

It is also an object of the invention to provide a boom stop arrangement which prevents the rapid and uncontrolled movement of the crane boom regardless of the position of the boom.

A further object of the invention is the provision of a crane boom stop arrangement in which the boom stop is effective to prevent the movement of the boom at all times except when the boom is being controllably raised or lowered.

A further object of the invention is the provision of a crane boom stop arrangement the operation of which is substantially unaffected by airborne grit, dirt, or moisture.

An additional object of the invention is the provision of a compression strut and link strut boom stop arrangement which includes means providing resiliency to absorb shock forces encountered during the sudden stopping of the boom.

Another object of the invention is the provision of a crane boom stop arrangement which is of simple construction but which is highly durable and capable of providing trouble free operation for sustained periods of time.

As will become apparent from the following detailed description of the invention, the above and other objects of the invention are achieved by providing a crane boom stop arrangement of the type employing a compression strut adopted to engage the boom at its maximum upper position and a link strut connecting the crane boom and the compression strut which includes braking means to prevent rotation of the link strut except when the boom is being controllably raised or lowered. By preventing movement of the link strut, the arrangement effectively locks the boom in any position by effectively making the compression strut and link strut arrangement into a rigid member in connecting the boom to the crane superstructure. It is contemplated that a tapered or multiple leaf spring may be incorporated into the link strut to provide the desired resiliency.

For a more complete understanding of the invention and the objects and advantages thereof reference should be had to the following specification and the accompanying drawings wherein there is shown a preferred embodiment of the invention.

In the drawing:

FIG. 1 is a side elevational view of a truck-mounted crane equipped with the boom stop arrangement of the present invention;

FIG. 2 is a fragmentary plan view of the crane of FIG. 1; FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a fragmentary sectional view taken along the line IV-IV of FIG. 1;

FIG. 5 is a fragmentary sectional view taken along the line V-V of FIG. 3;

FIG. 6 is a schematic showing of a control arrangement for the boom stop assembly of FIGS. 1-5; and

FIGS. 7 and 8 are side elevational views, partly in section, showing alternate arrangements for the link struts.

While reference is made in the following description to a truck-mounted crane, it will be understood that the invention is not so limited but rather may be employed with any boomtype crane in which it is desired to control the upward movement of the crane boom.

Referring now to FIGS. 1 and 2, there is shown a crane which consists generally of a base structure 10, a superstructure 12 which is rotationally mounted on the base structure 10 and which houses the boom elevating motors and winches, the lifting cable motors and winches, and the controls therefore, and a crane boom 14 pivotally mounted to the superstructure 12 for movement in a vertical plane. The boom portion 14 is comprised by a trusslike book 16 pivotally connected to the superstructure 12 by a suitable pin 18 and cable rigging 20 which is connected to the boom elevating winches to provide means for controllably raising and lowering the boom. A loadlifting cable 22 is also carried by the boom 16. All of the structure thus far described may be of conventional construction.

In order to provide an upper limit of boom travel and to provide means for controlling the movement of the boom below its upper limit, there is provided a boom stop arrangement designated generally by the reference numeral 24.

The boom stop arrangement includes a compression strut 26 which is connected at one end by a pin 28 to suitable trunnions 36 on the crane superstructure 12. The connection permits pivotal movement of the strut 26 about the axis of the pin 28. While not specifically shown, the mounting points for the trunnions 30 are obviously securely braced to the framing of the superstructure .12 so as to resist the substantial forces that may be encountered. Closely adjacent the upper or free end of the compression strut 26 there is connected a link strut 34. The connection between the compression strut 26 and the link strut 34 is a pivotal connection 32. The lower end of the link strut 34 is connected to the crane boom 16 by a pivotal connection indicated generally at 36.

The strut arrangement described above provides an upper limit of boom travel since the outer end of the compression strut 26 approaches the boom structure 16 as the boom is raised. A suitable end member 38 is provided on the free end of the compression strut 26 for engaging a stopblock 40 affixed to the upper edge of the boom I6. The compression strut 26 and the link strut 34 may be trusslike members, as shown in FIGS. 2 and 3, to withstand the substantial forces which may be encountered in controlling the movement of a long crane boom. Thus, the compression strut 26 may be provided with parallel siderails 42 and diagonal bracing 44 to form a rigid strut member. The link strut 34 likewise may have parallel side rails 46 and diagonal bracing 48.

Control of the boom in positions below the maximum boom elevation is provided by the brake arrangement shown in more detail in FIGS. 3 and 5. As is shown in these figures, the lower end of the link strut 34 is rigidly affixed to a rod 50 which is pivotally mounted to the upper rails 52 of the crane boom 16;

A brake assembly, designated generally as 54, is provided to control the rotation of the shaft 50. The brake assembly may be a conventional internal expanding drum type brake having backing plates 56 which are bolted or otherwise secured to the boom rails 52 and which mount brakeshoes 58, and brakedrums 60 which are affixed to and rotate with the shaft 50. Other types of brakes may be used if desired, for example, disc brakes may be employed in place of the internal expanding brakes. However, it is contemplated that conventional heavy-duty truck-type brake units may be employed for the brakes 54, thus considerably reducing the cost of the assembly as well as facilitating the maintenance and service of the units since parts are readily available for these conventional brake units.

Forming an important part of the invention is the control of the brake units which is designed to assure that the brakes are applied at all times except when the boom is being raised or lowered under operator control. One form of control is shown schematically in FIG. 6. In this arrangement the lever 62, which through the boom elevating controls controls the operation of the motors and winches which operate the boom elevating cables 20, is also connected to a valve 64 which, in its neutral position, supplies hydraulic fluid under pressure through a conduit 66 to the actuating cylinders 54a of the brake units 54. The valve is so designed that movement of the lever 62 in either the boom up or boom down direction interrupts the supply of fluid to the cylinders 54a and permits the release of pressure from these cylinders. This arrangement assures that the brake unit is applied at all times except when the operator has moved the control lever 62 to controllably raise or lower the boom. As a result, there is no possibility of the boom control inadvertently being left in an off or released position.

FIG. 7 illustrates a modified boom stop arrangement in which the link strut is formed in two sections, a rigid upper section 72 which is pivotally connected at 74 to the compression strut and a lower section 76 which consists of a leaf spring assembly connected by U-bolts 78 to the upper section 72 and, through a mounting plate 82, to the brake assembly 80 carried on the crane boom 16. Obviously, the leaf spring may be provided at the upper end of the link strut rather than at the lower end as illustrated, if desired. The embodiment shown in FIG. 8 employs a tapered spring link strut 84. In both of these embodiments the spring serves to provide resilience to the boom stop assembly to absorb a portion of the forces encountered during a sudden stopping of boom movement to prevent damage to the boom on the crane structure.

It will now be apparent that there has been provided a boom stop arrangement which not only prevents overbooming but which also prevents any rapid upward movement of the boom due to, for example, the snapping of a lifting cable when the boom is at less than its maximum elevation. Since the brakes are applied at all times when the boom is not being controllably raised or lowered, the forces which result when a cable breaks or the load is otherwise lost which would tend to move the boom upwardly are countered by the high static braking forces exerted between the brakeshoes 58 and the drums 60.

Should a cable break while the boom is being controllably raised or lowered, the operator need merely release the control lever 62. The brakes are then immediately applied and serve to dampen and retard the upward movement of the boom so that it does not reach its upward position at a high velocity.

It should be understood that changes and/or additions may be made in and to the described embodiment of the invention. Thus, for example, the brake assembly may be located at one of the other pivotal connections of the compression or link struts. The arrangement shown, however, is preferable since the link strut moves through a reater arch than does the compression strut. The scope of t e invention should be determined by reference to the following claims.

Iclaim:

l. A boom stop arrangement for controlling the upward movement of a boom pivotally connected at its lower end to the superstructure of a crane for movement in a vertical plane, comprising: a first strut pivotally connected at one end to the superstructure at a point remote from the boom connection; a second strut pivotally connected at one end to the boom at a point intermediate the ends thereof, the opposite end of the second strut being pivotally connected to the first strut at a point adjacent the free end thereof, the lengths of the first and second struts and the locations of the pivotal connections being such that the free end of the first strut contacts the boom when the boom is raised to a predetermined elevation; and controllable brake means at one of the strut pivot points to selectively prevent rotation of one of the struts about one of its pivotal axes.

2. The boom stop arrangement according to claim 1 wherein the brake means is mounted on the boom and is operable to prevent rotation of the second strut about the axis of its pivotal connection to the boom.

3. The boom stop arrangement according to claim 2 wherein the brake means comprises an internal expanding drum type brake unit.

4. The boom stop arrangement according to claim 3 wherein the nonrotating portion of the brake unit is rigidly secured to the boom and the rotating portion thereof is rigidly secured to an axle which forms the connecting member for the second strut.

5. The boom stop arrangement according to claim 1 wherein the brake means is controlled in coordination with the boom-elevating controls in such manner that the brake means is released only when the boom is being raised or lowered by the operator.

6. The boom stop arrangement according to claim 1 wherein the second strut comprises an elongated tapered spring.

7. The boom stop arrangement according to claim 1 wherein the second strut comprises a first nonresilient portion and a second resilient portion joined in generally end-to-end fashion.

8.'ln a crane having a superstructure, an elongated boom pivotally connected to the superstructure for movement in a vertical plane, and a boom stop arrangement comprised of a compression strut pivotally connected to the compression strut and to the boom, the improvement comprising: a friction brake assembly mounted on the boom and operable to controllably prevent rotation of the link strut about its pivotal connection to the boom.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,647,087

DATED 3 MARCH 7, 1972 |NVENTOR(5) I RALPH MOONEY It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 2, line 40, "book" should read -boom.

In column 4, line 58, following "the" insert superstructure and a link strut pivotally connected to the.

Signed and sealed this 29th day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A boom stop arrangement for controlling the upward movement of a boom pivotally connected at its lower end to the superstructure of a crane for movement in a vertical plane, comprising: a first strut pivotally connected at one end to the superstructure at a point remote from the boom connection; a second strut pivotally connected at one end to the boom at a point intermediate the ends thereof, the opposite end of the second strut being pivotally connected to the first strut at a point adjacent the free end thereof, the lengths of the first and second struts and the locations of the pivotal connections being such that the free end of the first strut contacts the boom when the boom is raised to a predetermined elevation; and controllable brake means at one of the strut pivot points to selectively prevent rotation of one of the struts about one of its pivotal axes.
 2. The boom stop arrangement according to claim 1 wherein the brake means is mounted on the boom and is operable to prevent rotation of the second strut about the axis of its pivotal connection to the boom.
 3. The boom stop arrangement according to claim 2 wherein the brake means comprises an internal expanding drum type brake unit.
 4. The boom stop arrangement according to claim 3 wherein the nonrotating portion of the brake unit is rigidly secured to the boom and the rotating portion thereof is rigidly secured to an axle which forms the connecting member for the second strut.
 5. The boom stop arrangement according to claim 1 wherein the brake means is controlled in coordination with the boom-elevating controls in such manner that the brake means is released only when the boom is being raised or lowered by the operator.
 6. The boom stop arrangement according to claim 1 wherein the second strut comprises an elongated tapered spring.
 7. The boom stop arrangement according to claim 1 wherein the second strut comprises a first nonresilient portion and a second resilient portion joined in generally end-to-end fashion.
 8. In a crane havIng a superstructure, an elongated boom pivotally connected to the superstructure for movement in a vertical plane, and a boom stop arrangement comprised of a compression strut pivotally connected to the compression strut and to the boom, the improvement comprising: a friction brake assembly mounted on the boom and operable to controllably prevent rotation of the link strut about its pivotal connection to the boom. 